Low voltage ignition system



Nov. 26, 1957 w. B. SMITS LOW VOLTAGE IGNITION SYSTEM Filed June 1, 1953 FIG.4

United States Patent 2,814,659 Low VOLTAGE IGNITION SYSTEM Wytze Beye Smits, Voorburg, Netherlands, assignor to Smitsvonk, N. V., Leidscliendam, Netherlands, a com- P y Application June 1, 1953, Serial No. 358,844

3 Claims. (Cl. 123-148) The invention relates to a low voltage ignition system for internal combustion engines, in which by means of an ignition coil a condenser is charged, which can discharge via a spark gap connected in series and one or more surface discharge spark plugs.

The Netherlands patent application No. 170,179 describes a similar system, by means of which the result is achieved that when the motor is started or runs at low speed, more than one spark is formed on the plug at each break, the number of sparks gradually decreasing with higher speeds to one spark per break at maximum speed. This is attained by adjusting the capacity of the coil, the size of the condenser, and the distance of the spark gap to one another within definite limits.

According to the present invention the effect achieved may even be enhanced and improved upon by increasing the distance of the spark gap at low speed, i. e. when the breaks are few, and by decreasing it at high speeds, since at low speeds the energy of the coil is greater than at high speeds.

This increase and decrease of the distance of the spark gap can be effected automatically according to the invention, so that this distance becomes automatically adjusted to the speed of the motor. In a multi-cylinder motor the distributor may serve as spark gap; this distributor may be so constructed that the distance between the rotating distributor contact and the fixed contacts varies automatically with the speed of the motor. In a one-cylinder motor, which therefore is not equipped with a distributor, there may be included in the discharge circuit a bimetal element or a heating wire or a magnet winding, by means of which the distance of the spark gap is adjusted in dependence on the speed of the motor, since in proportion to this speed a heavier or lighter current will flow through the primary winding, which will cause the bimetal element to bend more or less, cause the heating wire to expand more or less, or magnetize the magnet winding more or less strongly, which elements will then more or less displace one of the electrodes of the spark gap in relation to the other. These embodiments can naturally also be used in multi-cylinder motors.

When the ignition system is put in circuit, the heaviest current will flow through, and the distance of the spark gap will be greatest, so that the condenser will not be able to discharge until the voltage has become so high that the spark gap can break down. As the number of breaks increases, the strength of the current will grow smaller and smaller, and the capacity of the coil will decrease; since the motor is running, the ignition energy on the spark plug may now be smaller, as indeed it is, because now the voltage of the condenser need not rise to so high a value, while the distance of the spark gap has decreased, and it will therefore break down at a lower voltage as well. In this way, when the motor is started, several sparks are formed, which strike the oil layer off the spark plug and ignite the gas mixture, while with more frequent breaks, at which the coil energy is smaller, sufiicient ignition energy is still supplied to the plug, because the condenser can discharge via the spark gap with a smaller distance.

The invention will be explained more fully with reference to the drawing showing a number of embodiments.

Fig. 1 is a diagrammatic illustration of the system according to the invention, as applied to a four-cylinder motor.

Figs. 2, 3 and 4 are diagrammatic illustrations of embodiments according to the invention, as applied to a one-cylinder motor, which can, however, equally well be applied to a multi-cylinder motor, provided a distributor is included in the circuit.

In Fig. 1, the numeral 1 denotes the current-supplying source, which feeds the primary winding 4 of the ignition coil via the circuit breaker 2, which is shunted by a condenser 3. The secondary winding 5 is connected in parallel with the ignition condenser 6, one electrode of which is connected to earth and to the outer electrode of the spark plugs 7, while the other electrode is connected to the rotating arm 8 of the distributor, which moves past the fixed distributor contacts 9, which are connected to the central electrodes of the spark plugs 7. The rotating distributor arm 8 is constructed as a resilient arm, at the end of which is located, for example, the rotating distributor contact 10, which moves at a short distance past the fixed contacts 9, this distance depending on the speed of rotation of the arm 8. Thus, if the arm 8 rotates slowly, for example when the motor is started or runs at low speed, the distance between the contact 10 and the contacts 9 will be greater than when the motor runs at high speed, since in that case a greater centrifugal force is exerted thereon. The maximum defiection of the distributor arm 8 is delimited by a fixed stop 11.

Fig. 2 is a similar wiring diagram for a one-cylinder motor, in which the distance of the spark gap 12, 13 is magnetically controlled by means of a magnet 14, which, in dependence on the current flowing through, keeps the arm 12 at a greater or smaller distance from the fixed contact 13; the arm 12 is acted upon by a spring 15.

Fig. 3 is a similar wiring diagram, but here the spark gap 16, 17 is controlled by the greater or smaller expansion of a heating wire 18, which is connected via a spring 19 to the rotatable arm 20 of the spark gap.

Finally, Fig. 4 illustrates an embodiment with a bimetal element 21, 22, which is acted upon by a tension spring 23 and bends more or less in dependence on the primary current flowing through, thus controlling the dis tance between 21 and 22.

I claim:

1. In a low voltage ignition system for internal combustion engines an ignition coil, an ignition condenser connected in parallel with said coil, a discharge circuit for said condenser, said discharge circuit including a plurality of low voltage surface discharge spark plugs and a distributor having a movable contact and a plurality of fixed contacts connected in series with said spark plugs, and means on said distributor for automatically varying the distance between said movable contact and said fixed contacts wherein said distance is dependent on the speed of the engine.

2. A low voltage ignition system as claimed in claim 1 wherein said last named means comprises a resilient arm on said distributor.

3. A low voltage ignition system as claimed in claim 2 including a stop to limit movement of said resilient arm.

References Cited in the file of this patent UNITED STATES PATENTS 791,856 Apple June 6, 1905 1,370,077 Whisler Mar. 1, 1921 1,537,903 Von Lepel May 12, 1925 2,284,068 Roberts May 26, 1942 

